Summary:
Passive acoustic noise logging is an oil and gas production surveillance technique. It is used mainly to locate fluid inflow intervals and to detect behind-the-casing flow. Permanent logging techniques improvement motivates further studies of acoustic noise excited in the formation. Analysis of noise in the borehole offers potential for locating formation inflow boundaries, and specifically for detecting the pay zone. However, the acoustic fields depend not only on the excitation signal but also on the reservoir properties and geometry. In this paper, the influence of these parameters on the acoustic field spectrum along the wellbore is investigated in the presence of a noise source in the formation. Examples of a gas-producing layer and water breakthrough in the oil reservoir are considered. Using numerical modeling of the acoustic field in the near-wellbore zone, it is shown the significant signal amplification at frequency intervals corresponding to the resonant modes of the borehole. At the same time, the resonances do not prevent detecting boundaries of the pay-zone or identifying high-permeability channels.